The Great Mars Rush

The Great Mars Rush

Hurtling toward Mars at 22,000 mph, Earth is heading
for its closest encounter with the Red Planet in a dozen years.

Once in about every fifteen years a startling visitant
makes his appearance upon our midnight skies --a great red star
that ... mounting higher with the deepening night, blazes forth
against the dark background of space with a splendor that outshines
Sirius and rivals the giant Jupiter himself. -- from Mars
by Percival Lowell (1895)

May
15, 2001 -- By the time you finish reading this sentence,
you'll be 50 kilometers closer to the Red Planet.

Earth and Mars are converging at 10 km/s (22,000 mph) as the
pair head for a close encounter next month. On June 21st Mars
will lie just 68 million km from Earth -- the nearest it's been
in a dozen years.

"The next few months will be a great time to look at
Mars," says astronomy professor George Lebo, a NASA Summer
Faculty Fellow at the Marshall Space Flight Center. "You
won't need a telescope to see it. By early June Mars will outshine
everything except Venus, the Moon, and the Sun itself ."

Mars is already a brilliant morning star. Early rising observers
in the northern hemisphere can spot the Red Planet about 30 degrees
above the southern horizon. Sky watchers south of the equator
will see Mars arcing high overhead before dawn. In either hemisphere,
the planet is easy to pick out near the spout of the teapot-shaped
constellation Sagittarius. Mars is bright and doesn't twinkle
like a real star -- its steady copper-hued gaze is unmistakable.

In the weeks ahead the Red Planet will grow even brighter
as it approaches opposition on June 13th, the date when Earth
and Mars are lined up on the same side of the Sun. Astronomers
call the arrangement opposition because Mars and the Sun
will lie on opposite sides of our planet's sky. Mars is
at opposition once every 26 months.

If
the orbits of Mars and Earth were perfectly circular, then the
distance between two planets would be least at the moment of
opposition. But that's not the case. Earth's orbit is slightly
elliptical and the martian orbit is substantially more so. As
a result, our closest approach to Mars won't happen until eight
days later on June 21st.

Left: Mars is "at opposition" when it lines
up with Earth on the same side of the Sun.

By that time Mars will no longer be a morning star -- it'll
be a dazzling "all-nighter," rising near sunset and
reaching its highest point in the sky at midnight. Modest telescopes
will reveal normally invisible details including martian clouds
and icy polar caps. See Sky and Telescope's "A
Grand Return of Mars" for more information.

Throughout the coming months Mars will linger in a region
of the sky that's home to the very center of our galaxy. This
will be a treat for dark sky observers who can see the faint
Milky Way, a hazy band of stars that bisects the sky along the
galactic plane. The Milky Way cuts through Sagittarius and brightens
near the spout of the teapot -- right by Mars! There lies the galactic
center, the lair of a supermassive black hole around which
our entire pinwheel galaxy spins.

Despite their proximity in the sky, Mars and the galactic
center are really very far apart. A spacecraft from Earth traveling
at light speed would arrive at the Red Planet in only a few minutes.
Reaching the inner regions of our galaxy would take an extra
30,000 years!

Above: This annotated map of the constellation Sagittarius
shows the galactic center and the approximate location of Mars
in mid-May. The galactic center lies behind a think veil of absorbing
dust in the galactic plane. Nearby "Baade's Window"
is a relatively dust-poor region that allows some of the light
from the innermost galaxy to shine through. Click to enlarge.

If spacecraft could travel at the speed of light, we could
visit Mars any time we wished. However, NASA's advanced propulsion
systems aren't yet that advanced. We have to choose our
opportunities carefully and visit Mars when the planet is nearby
-- in other words, at opposition.

NASA's latest Mars probe, 2001 Mars Odyssey, blasted
off on April 7th and it's hurtling toward the Red Planet even
faster than we are. Earth's approach will slow and then reverse
as Mars reaches opposition in June, but Mars Odyssey will continue
until it enters Mars orbit on October 24th. During the probe's
two and a half year mission, it will monitor space radiation,
seek out underground water, and identify interesting minerals
on the martian terrain.

Because of Mars' eccentric orbit, not all oppositions are
alike. At the next one, on August 28, 2003, Mars and Earth will
be just 56 million km apart -- closer than any opposition since
1924. It will be the perfect time to send a new batch of robotic
explorers to Mars. Indeed, NASA plans to launch a pair of Mars
Exploration Rovers in 2003, and the European Space Agency
will send a lander of its own, the Beagle
2, which will ride to Mars on board the Mars
Express Mission.

Favorable oppositions of Mars recur with a 15-to-16 year cycle.
Perhaps the series of close encounters 15 years from now could
be our first opportunity to send humans to the Red Planet!

Meanwhile, don't miss the ongoing show. Mars is out there
now, fiery red and beckoning from your own back yard!

Above: The southern sky shortly before dawn on May 15,
2001. Copper-hued Mars shines at visual magnitude -1.5 between
the constellations Sagittarius and Scorpius. Don't confuse Mars
with Antares ("anti-Mars"), the red first magnitude
star in Scorpius.

Web Links

Why
2003? -- This site from the European Space Agency explains
why we launch spacecraft to Mars during opposition, and why some
oppositions are better than others.

The Science and Technology Directorate at NASA's
Marshall Space Flight Center
sponsors the Science@NASA web sites. The mission of Science@NASA is to
help the public understand how exciting NASA research is and to help
NASA scientists fulfill their outreach responsibilities.